Hippocampal-dependent appetitive control is impaired by experimental exposure to a Western-style diet

Animals fed a Western-style diet (WS-diet) demonstrate rapid impairments in hippocampal function and poorer appetitive control. We examined if this also occurs in humans. One-hundred and ten healthy lean adults were randomised to either a 1-week WS-diet intervention or a habitual-diet control group. Measures of hippocampal dependent learning and memory (HDLM) and of appetitive control were obtained pre- and post-intervention. HDLM was retested at 3-weeks follow-up. Relative to controls, HDLM performance declined in the WS-diet group (d=0.43), but was not different at follow-up. Appetitive control also declined in the WS-diet group (d=0.47) and this was strongly correlated with HDLM decline (d=1.01). These findings demonstrate that a WS-diet can rapidly impair appetitive control in humans - an effect that could promote overeating in consumers of a WS-diet. The study also suggests a functional role for the hippocampus in appetitive control and provides new evidence for the adverse neurocognitive effects of a WS-diet

A high-fat high-sugar diet predicts poorer hippocampal-related memory and a reduced ability to suppress wanting under satiety

Animal data indicate that greater intake of fats and sugars prevalent in a Western diet impairs hippocampal memory and tests of behavioral inhibition known to be related to hippocampal function (e.g., feature negative discrimination tasks). It has been argued that such high fat high sugar diets (HFS) impair the hippocampus, which then becomes less sensitive to modulation by physiological state. Thus retrieval of motivationally salient memories (e.g., when seeing or smelling food) occurs irrespective of state. Here we examine whether evidence of similar effects can be observed in humans using a correlational design. Healthy human participants (N = 94), who varied in their habitual consumption of a HFS diet, completed the verbal paired associate (VPA) test, a known hippocampal-dependent process, as well as liking and wanting ratings of palatable snack foods, assessed both hungry and sated. Greater intake of a HFS diet was significantly associated with a slower VPA learning rate, as predicted. Importantly, for those who regularly consumed a HFS diet, while reductions in liking and wanting occurred between hungry and sated states, the reduction in wanting was far smaller relative to liking. The latter effect was strongly related to VPA learning rate, suggestive of hippocampal mediation. In agreement with the animal literature, human subjects with a greater intake of a HFS diet show deficits in hippocampal-dependent learning and memory, and their desire to consume palatable food is less affected by physiological state – a process we suggest that is also hippocampal related

The Role of Disgust in Male Sexual Decision-Making

Sexual arousal is known to increase risky behaviors, such as having unprotected sex. This may in part relate to the emotion of disgust, which normally serves a disease avoidant function, and is suppressed by sexual arousal. In this report we examine disgust's role in sexual decision-making. Male participants received two study packets that were to be completed at home across two different time-points. Participants were asked to complete one packet in a sexually aroused state and the other in a non-aroused state. Participants were asked to rate: (1) arousal, (2) disgust, (3) willingness for sex, and (4) disease risk toward a range of female targets, which varied in level of potential disease risk (sex-worker vs. non sex-worker) and attractiveness. A measure of trait disgust was also included along with other related scales. Sexual arousal was associated with reduced disgust and reduced judgments of disease risk for all targets—these latter two variables being correlated—and with enhanced willingness to have sex with all of the depicted persons. Willingness to have sex when aroused (in contrast to non-aroused) was predicted by disease risk judgments and trait disgust, suggesting both direct (state) and indirect (trait) effects of disgust on sexual decision-making

Chemosensory abilities in consumers of a western-style diet

People vary in their habitual diet and also in their chemosensory abilities. In this study we examined whether consumption of a Western-style diet, rich in saturated fat and added sugar, is associated with either poorer or different patterns of chemosensory perception, relative to people who consume a healthier diet. Participants were selected based on a food frequency questionnaire, which established whether they were likely to consume a diet either higher or lower in saturated fat and added sugar. Eighty-seven participants were tested for olfactory ability (threshold, discrimination, identification), gustatory ability (PROP sensitivity, taste intensity, quality and hedonics), and flavour processing (using dairy fat-sugar-odour mixtures). A Western-style diet was associated with poorer odour identification ability, greater PROP sensitivity, poorer fat discrimination, different patterns of sweetness taste enhancement, and hedonic differences in taste and flavour perception. No differences were evident for odour discrimination or threshold, in perception of taste intensity/quality (excluding PROP) or the ability of fats to affect flavour perception. The significant relationships were of small to moderate effect size, and would be expected to work against consuming a healthier diet. The discussion focuses on whether these diet-related differences precede adoption of a Western-style diet and/or are a consequence of it

Sweet odours and sweet tastes are conflated in memory

Certain odours and certain tastes appear to share common perceptual properties. One example is sweetness, a perceptual experience that results from stimulation of taste receptors on the tongue typically by sugars. The experiment here examined for evidence of this perceptual similarity using a novel and indirect test. Participants were exposed six times each, to three odours (strawberry, caramel, and oregano) and three tastes (sucrose, saline, and citric acid). Following a 10-min interval, participants were given a surprise frequency estimation task, in which they had to judge how often each stimulus had occurred. If sweet-smelling strawberry and caramel odours really do share this perceptual characteristic in common with sweet tasting sucrose, then frequency estimates for sucrose should be overestimated relative to non-sweet tastes. Not only was this observed, but frequency estimates for sweet tastes were also found to correlate with (1) evaluations from a later test of similarity between these sweet smells and sucrose, and (2) the degree to which these odours smelled sweet. These findings suggest a shared perceptual feature between such odours and sucrose – sweetness – under conditions where no judgment of perceptual quality was required.5 page(s

The Development of disgust

11 page(s

Disgust and moral judgment

24 page(s

Disease avoidance as a functional basis for stigmatization

Stigmatization is characterized by chronic social and physical avoidance of a person(s) by other people. Infectious disease may produce an apparently similar form of isolation-disease avoidance-but on symptom remission this often abates. We propose that many forms of stigmatization reflect the activation of this disease-avoidance system, which is prone to respond to visible signs and labels that connote disease, irrespective of their accuracy. A model of this system is presented, which includes an emotional component, whereby visible disease cues directly activate disgust and contamination, motivating avoidance, and a cognitive component, whereby disease labels bring to mind disease cues, indirectly activating disgust and contamination. The unique predictions of this model are then examined, notably that people who are stigmatized evoke disgust and are contaminating. That animals too show avoidance of diseased conspecifics, and that disease-related stigma targets are avoided in most cultures, also supports this evolutionary account. The more general implications of this approach are then examined, notably how it can be used to good (e.g. improving hygiene) or bad (e.g. racial vilification) ends, by yoking particular labels with cues that connote disease and disgust. This broadening of the model allows for stigmatization of groups with little apparent connection to disease.20 page(s

The Role of attention in the localization of odors to the mouth

Odors can be perceived as arising from the environment or as part of a flavor located in the mouth. One factor that may dictate where an odor is perceived to be is concurrent gustatory stimulation in the mouth. A taste may impair the ability to attend to an odor, especially if they are perceptually similar. Alternatively, salient mouth-based features of a flavor might command attention at the expense of smell. Experiment 1 and 2, using different stimulus sets, explored the impact of perceptually similar and dissimilar pairings of tastes in the mouth and odors at the nose. In each case, these were followed by judgments of the odor’s location (mouth vs. nose). Perceptual similarity had no impact on localization judgments. Experiment 3 then manipulated the salience of the olfactory and gustatory cues and showed that each could independently shift the perceived location of an odorant—salient olfactory cues toward the nose and gustatory cues toward the mouth. These findings suggest that the salient features of a flavor may command attention at the expense of olfaction and, thereby, contribute to oral localization, with implications for flavor binding.12 page(s

The Role of taste and oral somatosensation in olfactory localization

Although there is only one set of olfactory receptors, odours are experienced as smells when sniffing things (e.g., sniffing a wine's bouquet) and as flavours when the olfactory stimulus is present in the mouth (e.g., drinking wine). How this location binding-external versus internal environment-is achieved is poorly understood. Experiment 1 employed a new procedure to study localization, which was then used to explore whether localization is primarily dependent upon simultaneous oral somatosensation. Experiment 2, using solutions of varying viscosity, and Experiment 3, using oral movement of varying vigour, revealed that sniffed odours are not localized to the mouth by somatosensation alone. Instead, Experiment 4 demonstrated that a tastant needs to be present and that increasing tastant concentration generates increasing oral localization. Experiment 5 found that this reliance upon gustation reflects the previously observed "confusion" that people show for taste and smell stimuli in the mouth. We suggest that this "confusion" reflects the gustatory system's superior ability to suppress olfactory attention, thus assisting flavour binding.17 page(s